Each year millions of humans die from water borne pathogens. One statistic quoted by The World Bank, The World Health Organization, and the Harvard School of Public Health, among others, is that 1.8 million children die each year from simple, preventable cases of diarrhea which are caused by drinking water contaminated with pathogens. The human toll equates to over 200 children's lives lost per hour, and nearly 5,000 per day. This is mostly an issue within the developing regions, but also can become an issue in industrialized nations in times of war, or natural disasters such as floods, earthquakes, tsunamis, or any time civil unrest or terrorism disrupts centrally distributed and disinfected tap water, whose systems often rely heavily on chemicals and electric power.
It is known that direct solar radiation is one energy source that is capable of disinfecting water. There are numerous methods and devices for direct solar-based water disinfection; these usually utilize one or more bands of naturally-occurring radiation comprised of thermal (infrared), visible, and/or ultraviolet light energy. The thermal disinfection mechanism is characterized by sufficiently heating the water for some minimum duration and at some minimum temperature to induce pasteurization of the water. The non-thermal disinfection mechanism is characterized by sufficiently exposing the DNA and/or RNA of micro-organisms to photon energies that can impart direct dissociation of the chemical compounds that are the “building blocks” of the DNA/RNA chain, thereby breaking the cellular replication cycle and continued growth of the organism. While it is possible to perform disinfection with large amounts of visible light photons, the increasingly higher photon energy of shorter wavelength ultraviolet light photons produces much greater disinfection in terms of pathogen log reduction per unit average fluence of light exposure. This is why ultraviolet light within the UV-C band (wavelength ˜210 nm to ˜290 nm, also known as the “disinfection band”) is most efficacious and preferred. However, for the purpose of terrestrial-based direct solar disinfection applications, because only small amounts of UV-C band ultraviolet light passes from the sun to below the upper atmosphere, the non-thermal mechanism is practically limited to the less-energetic photons comprising the UV-A band (wavelengths 320-400 nm) and the UV-B band (wavelengths 290-320 nm). Herein we shall refer collectively to these bands as “broadband UV”.
There exists a well-known, simple, very low-cost, and effective solution that can save lives by purifying the water using natural sunlight; this is known as the SODIS (SOlar DISinfection) method. The effectiveness of the SODIS method was first discovered by Professor Aftim Acra at the American University of Beirut in the early 1980s. Additional research was conducted by the research groups of Martin Wegelin at the Swiss Federal Institute of Aquatic Science and Technology (Eawag) and Dr Kevin McGuigan at the Royal College of Surgeons in Ireland. Clinical control trials were pioneered by Professor Ronan Conroy of the RCSI team in collaboration with Dr. T. Michael Elmore Meegan.
A simple explanation of the standard SODIS method is as follows:
1) Fill an ultraviolet-transparent P.E.T. plastic bottle about half to three quarters full of relatively “clear” water. For example, this might require that the water first be pre-filtered with a simple sand filter composed of a layer of gravel, sand, and perhaps charcoal. None-the-less, this water still may contain deadly pathogens.
2) Cap the bottle tightly.
3) Shake the bottle for at least 30 seconds, thereby importantly mixing in some oxygen, and subsequently increasing the oxidizing potential to the water, thus enhancing the efficacy of the available sunlight.
4) Expose the bottle to full sunlight for at least 6 hours. An additional process enhancement is to place the bottle atop a corrugated metal surface, so that some sunlight will be reflected back, thereby creating two passes through the water.
5) The water should then be free of dangerous biological pathogens.
The SODIS method treats the contaminated water through several synergistic mechanisms: radiation in the spectrum of UV-A (as well as a lesser amount of radiation in the UV-B spectrum), increased water temperature, and some limited oxidation from the interaction of ultravioletT with dissolved oxygen. It has been shown that if the water temperature rises to as little as 50° C., the disinfection process is three times faster than otherwise achievable without the thermal enhancement mechanism.
There are, however, several problems and short-comings with the SODIS method of water disinfection. There is no effective way to positively validate that the water contained in a bottle treated by the SODIS method has indeed been disinfected. There is no appropriate feedback mechanism, safety/security seal, or quality control of any kind. Many people may be suspicious of lower technology solutions. As a result, they will not use the water for any means, preferring to spend scarce third world income on bottled water, even if that sealed bottle represents more than a day's wage. This means that in many cases, unfortunate parents make an agonizing choice between guaranteeing their family's health by spending their limited income on expensive bottled water, or else incur a potentially life threatening risk by using water from an unreliable source, thereby saving the onerous expense of bottled water.
An additional liability of standard SODIS technology is a side-effect of one of its otherwise advantages: it utilizes used P.E.T. plastic bottles, so encourages re-use while providing an essentially no-cost source of containers. The detrimental side of this, however, is that recent evidence shows that heating plastic-bottled water is a potentially unsafe practice, due to the release from the plastic of cancer-causing and endocrine-disrupting compounds. So, the more immediate life-saving benefits of SODIS water treatment are compromised by the long-term risk effects of chemical poisoning.
A device that provides a limited measure of disinfection process efficacy confirmation is a reusable low-melting temperature wax-based Water Pasteurization Indicator (WAPI), typically costing $5 to $10. Note that this is an entirely thermal energy-based (that is, pasteurization) indicator, and must first be inserted into the bottle prior to pasteurization, then removed by its string tether prior to utilizing the water. Therefore, the combination of expense, complexity, lack of permanent and fail-safe security, and subsequent re-contamination risk is problematic, the WAPI is therefore considered by some to not be a compelling technology that fulfills the requirements for wide-spread implementation.
In order for SODIS-based treatment to realize its full potential and provide less-fortunate families with a simple, yet compelling solution to their potable water needs, there is therefore a need to solve the issues now identified as problematic and adverse to the widespread implementation of SODIS.
Wadstrom (U.S. Pat. No. 7,837,865) discloses a device using a combination of solar heat and ultraviolet, however, there is no ultraviolet disinfection (nor Pasteurization) indication mechanism, nor does is there a means by which a user will know they are in receipt of a securely sealed container.
Funken (U.S. Pat. No. 6,633,042) discloses a solar-based photobioreactor claimed effective for water disinfection, however the photobioreactor is not suitable as a portable container, nor does it provide for a securely sealed container or an indication of disinfection efficacy.
The invention disclosed herein provides the methods and means by which one may benefit from SODIS-type water disinfection that is uniquely and inherently fail-safe, thereby confirming to the user that the bottle contents are secure, safe, and healthful for human consumption. An additional (and complimenting) benefit of this invention is socio-economic in nature, in that it enables the establishment of a wide network of very local, grass-roots-based entrepreneurial endeavors, all based upon the need to create, distribute, sell, and recycle/support the ensuing products. This is a resource that supplies a local solution to a local problem.